My wife was banned a bit before more. She sold one textbook and fulfilled the transaction perfectly. She found out she was banned when they said they were keeping her money for 45 days, and they would be kind enough to release it to her if the buyer confirmed receipt of the book (they did, and she did get her money eventually).
Based on the mail that was arriving, we _think_ that someone who lived at our apartment before us was doing something shady. Amazon doesn't care though.
This kind of thing is why it's incredibly frustrating that people blithely let a few companies control most commerce.
Admittedly, we at least had recourse, while you don't for whatever reason, in the event that you one day do want to become a marketplace seller. My point is that it's really easy to get blacklisted. Perhaps it's because they prefer to have some false positives, rather than deal with real bad actors. Just a conjecture.
Might be $500 max for the court fees.
Then they eventually have to explain it and litigate with you. And eventually revise their ridiculous CS practices.